How to write a shell script that runs some commands as superuser and some commands not as superuser, without having to babysit it?

Question

I want to write a shell script to automate a series of commands. The problem is some commands MUST be run as superuser and some commands MUST NOT be run as superuser. What I have done so far is something like this: ``` #!/bin/bash command1 sudo command2 command3 sudo command4 ``` The problem is, this means somebody has to wait until command1 finishes before they are prompted for a password, then, if command3 takes long enough, they will then have to wait for command3 to finish. It would be nice if the person could get up and walk away, then come back an hour later and be done. For example, the following script has this problem: ``` #!/bin/bash sleep 310 sudo echo "Hi, I'm root" sleep 310 sudo echo "I'm still root?" ``` How can I make it so that the user can just enter their password once, at the very start, and then walk away? Update: Thanks for the responses. I'm running on Mac OS X Lion and ran Stephen P's script and got different results: (I also added $HOME) ``` pair@abbey scratch…

Accepted Answer

File `sutest`

```
#!/bin/bash
echo "uid is ${UID}"
echo "user is ${USER}"
echo "username is ${USERNAME}"
```

run it: `./sutest' gives me

```
uid is 500
user is stephenp
username is stephenp
```

but using sudo: `sudo ./sutest` gives

```
uid is 0
user is root
username is stephenp
```

So you retain the original user name in $USERNAME when running as sudo. This leads to a solution similar to what others posted:

```
#!/bin/bash
sudo -u ${USERNAME} normal_command_1
root_command_1
root_command_2
sudo -u ${USERNAME} normal_command_2
# etc.
```

Just sudo to invoke your script in the first place, it will prompt for the password once.

I originally wrote this answer on Linux, which does have some differences with OS X

OS X (I'm testing this on Mountain Lion 10.8.3) has an environment variable `SUDO_USER` when you're running sudo, which can be used in place of `USERNAME` above, or to be more cross-platform the script could check to see if SUDO_USER is set and use it if so, or use USERNAME if that's set.

Changing the original script for OS X, it becomes...

```
#!/bin/bash
sudo -u ${SUDO_USER} normal_command_1
root_command_1
root_command_2
sudo -u ${SUDO_USER} normal_command_2
# etc.
```

A first stab at making it cross-platform could be...

```
#!/bin/bash
#
# set "THE_USER" to SUDO_USER if that's set,
#  else set it to USERNAME if THAT is set,
#   else set it to the string "unknown"
# should probably then test to see if it's "unknown"
#
THE_USER=${SUDO_USER:-${USERNAME:-unknown}}

sudo -u ${THE_USER} normal_command_1
root_command_1
root_command_2
sudo -u ${THE_USER} normal_command_2
# etc.
```

How to write a shell script that runs some commands as superuser and some commands not as superuser, without having to babysit it?

Solution

Problem